The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

New car search powers for NT police

Northern Territory police will soon be able to declare major highways "drug transit routes" and search cars at random in an effort to slow the interstate flow of drugs, the government says.

On Tuesday, Chief Minister Adam Giles announced the proposed changes to the Misuse of Drugs Act, which would permit police to declare main arterial roads such as the Stuart, Barkly or Victoria Highways drug transit routes for 14 days, and then stop and search cars they suspect of carrying drugs without a warrant.

Police already have the power to search and seize alcohol and kava heading into indigenous communities, and the new laws are an expansion to target traffickers.

Mr Giles said 80 per cent of illicit drugs in the NT are trafficked from interstate, particularly along those roads.

He hopes the new law will help reduce the supply and therefore levels of addiction, particularly to methylamphetamine, or ice.

"Ice ... is a scourge on our society, as we all know; It provides substantial harms to individuals, to users and to the community in general, and is the source of serious levels of crime," he said.

When asked what checks and balances would be in place to ensure police did not abuse the new powers, Mr Giles said: "There's a high degree of transparency and accountability in the police force in the NT and they have my full support.